Conventional ultrahigh-pressure fluid systems have been used to pressurize pumpable substances, such as foods and slurries. For example, conventional ultrahigh-pressure systems have been used to improve the quality and longevity of food by subjecting the food to pressures in excess of 10,000 psi. Conventional systems have also been used to pressurize abrasive slurries to ultrahigh-pressure levels. The slurries can then be directed toward a substrate in the form of a liquid jet to cut the substrate or treat the surface of the substrate.
One conventional system includes a high-pressure cylinder with a slidable piston that divides the cylinder into two regions. The pumpable substance is placed in one region while a high-pressure fluid is introduced into the other region, driving the piston against the pumpable substance at a very high pressure. One potential drawback with this system is that as the piston may require specially designed seals to prevent the high-pressure fluid from being transported by the piston into the pumpable substance region. The seals may require periodic monitoring and replacement. Accordingly, it may be desirable to use an improved apparatus for pressurizing a pumpable substance while reducing the likelihood for contact between the pumpable substance and the pressurizing liquid.